1. Field of the Invention
The present invention relates to a tension detection mechanism configured to detect the tension of a linear member such as a wire (the force of a joint portion) in a drive device which drives the joint portion by using the tension of the linear member, and a manipulator using the tension detection mechanism.
2. Description of the Related Art
When performing an abdominoscopic operation or pneumoscopic operation, an operator makes a small hole in the abdominal region of a patient and places a jig called a trocar in the hole in an inserted state. The operator then inserts a medical manipulator having a joint portion at the working portion of the distal end into the body of the patient through the insertion hole of the trocar, and performs an intraabdominal operation by operating the acting portion provided closer to the distal end than the joint portion. In general, since the diameter of the insertion hole of the trocar is 10 mm or less, the diameter of the tubular portion of a manipulator inserted through the trocar is required to be smaller than that of the trocar. As a manipulator having a tubular portion which is thin (a diameter of 10 mm or less) and long (a length of 300 mm or more), there is available a multi-degree-of-freedom manipulator typified by the da Vinci system available from Intuitive Surgical.
To meet the requirement to reduce the diameter of a tube portion, a linear member such as a wire is used as a power transmission member which transmits power from a motor as a joint portion drive mechanism to the joint. For example, a da Vinci system manipulator uses a linear member such as a wire having a small diameter of about 0.5 mm to place a power transmission member in a limited space inside a tube portion having a diameter of 10 mm or less.
Japanese Patent No. 3727937 and U.S. Patent Application Publication No. 2007/0151391 disclose medical manipulators. The working portion of such a manipulator is provided with a force detection mechanism configured to detect the force of a joint portion. The force detection mechanism includes a strain gauge as a detection member attached to the working portion. The strain gauge detects the force of the joint portion by detecting an external force acting on the working portion.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 2006-263849 discloses a tension detection mechanism configured to detect the tension of a linear member. This tension detection mechanism has a load cell provided for one of a plurality of pulleys which guide the linear member. The load cell is used to detect the tension of the linear member.